Electrostatic recording using discharge space potential

ABSTRACT

An electrostatic recording device utilizes the scanning action of an electric glow discharge and the resulting gaseous conduction. The discharge current is controlled in response to a video signal. Spatial scanning is provided by a plurality of scanning electrodes spaced apart from a common electrode and sequentially pulsed to establish a progressing gas discharge. A plurality of stylus electrodes are each responsive to the gas discharge between a respective scanning electrode and the common electrode to produce a facsimile recording or the like.

United States Patent [191 Ohkubo Mar. 11, 1975 ELECTROSTATIC RECORDING USING DISCHARGE SPACE POTENTIAL [75] lnventor: Toshio Ohkubo, Tokyo, Japan [73] Assignee: Nippon Electric Company, Limited,

Tokyo, Japan [22] Filed: Aug. 20, 1973 [21] Appl. No.: 389,743

[30] Foreign Application Priority Data Aug. 22, 1972 Japan 47-8428] [52] US. Cl 346/74 ES, 178/6.6 A, 346/74 S [51] Int. Cl. G0ld 15/06 [58] Field of Search 346/74 E, 74 ES, 74 S,

346/74 SB, 74 SC; l78/6.6 A; 313/196 [56] References Cited UNITED STATES PATENTS 3,209,324 9/1965 Diamond et al 179/1002 MD 555G555 waver-pour 3,750,190 7/1973 Ohkubo et a1. 340/74 ES Primary Examiner-Terrell W. Fears Assistant Examiner-Jay P. Lucas Attorney, Agent, or Firm-Sughrue, Rothwell, Mion, Zinn 8L MacPeak [57] ABSTRACT An electrostatic recording device utilizes the scanning action of an electric glow discharge and the resulting gaseous conduction. The discharge current is controlled in response to a video signal. Spatial scanning is provided by a plurality of scanning electrodes spaced apart from a common electrode and sequentially pulsed to establish a progressing gas discharge. A plurality of stylus electrodes are each responsive to the gas discharge between a respective scanning electrode and the common electrode to produce a facsimile recording or the like.

5 Claims, 4 Drawing Figures BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to an electrostatic recording device and, more particularly, to a new and improved electrostatic recording device for use in a facsimile recording apparatus and the like.

2. Description of the Prior Art Conventional electrostatic recording devices are classified into two categories: one using mechanical scanning multi-stylus electrodes and the other using an electrostatic printing tube.

The former, the multi-stylus electrode type, which relies upon mechanical scanning, has the disadvantages that its scanning speed is not very high, being of the order of 1,000 lines per minute at most, and that it requires frequent maintenance necessitated by the need for frequent replacement of rotary brushes, which are for distributing video signals to multi-stylus electrodes, and the multi-stylus electrodes themselves, both of which can be easily worn out during operation.

An electrostatic printing tube has an inherently high scanning speed, because the deflection of an electron beam is utilized for scanning. This electron tube, however, is inevitably expensive because of its particular construction. Another disadvantage is that extremely high voltages of the order of 15 kilovolts are needed for operation. Still another disadvantage of the electrostatic printing tube is the high dielectric strengths required for the components of peripheral circuitry because of the grounded-anode type circuit structure. A further disadvantage is the complex adjustment procedure required in the tube manufacture, such as exact electron beam focussing, compensation for deflection uniformity, etc.

SUMMARY OF THE INVENTION In contrast to these conventional recording devices, this invention utilizes the electric glow discharge phenomenon, which has been used for display devices, to provide an electrostatic recording device which utilizes the scanning action of an electric discharge and the resulting gaseous conduction.

The present invention has made a great contribution to the solution of the problems of the prior art by realizing an extremely compact electrostatic recording device which features low manufacturing cost, ease of maintenance, and high scanning speeds.

It is one object of this invention to provide a unique, hermetically enveloped electrostatic recording device which overcomes the limitations unavoidable with the prior art, by incorporating means for controlling a discharge current in response to the video signals, thereby reducing the possibility of the occurrence of sputtering to a minimum and eventually contributing to an extended life of the recording device.

It is another object of the present invention to provide a unique, hermetically enveloped electrostatic recording device of extreme structural compactness due to the utilization of IC techniques, resulting in case, precision, and economy of fabrication.

Among the outstanding advantages of the electrostatic recording device according to the invention over the prior art devices are extremely high scanning speed, low operating voltages of the order of less than 1 kilovolt, uniform scanning speed due to the adoption of regular repetition scanning pulses, and the dispensability of complex peripheral circuitry.

BRIEF DESCRIPTION OF THE DRAWINGS These, and other objects and features of the present invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic diagram illustrating the principles of operation of an electrostatic recording device according to this invention;

FIG. 2 is a perspective view' of a typical electrode arrangement for an electrostatic recording device according to this invention;

FIG. 3 is a schematic circuit diagram for example of a variable resistance element for use in the electrostatic recording device of this invention;

FIG. 4 is an exploded perspective view depicting the detailed construction of an embodiment of the electrostatic recording device of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, the recording device comprises a hermetically sealed envelope containing therein an inert gas such as neon, argon, or xenon or their mixture at a predetermined pressure, a plurality of scanning electrodes 111 through 117 and so forth in coplanar array disposed in the envelope at regular intervals, a common electrode (anode) disposed in the envelope at a suitable spacing with respect to the array of scanning electrodes, and a plurality of voltage pickup electrodes 121 through 127 and so forth also" in coplanar array disposed adjacent said array of scanning electrodes in one-to-one correspondence.

To these voltage pickup electrodes 121 through 127 and so forth are connected respectively the recording stylus electrodes, 131 through 137 and so forth in oneto-one correspondence, which extend outwardly from the hermetically sealed envelope 100 so as to be aligned at equal intervals and to come in contact with an electrostatic recording medium such as paper which travels at a uniform speed on the backing electrode in a direction normal to the surface of the drawing.

Of the plurality of the scanning electrodes, the scanning electrode 111 is connected to the scanning terminal 16l-provided outside of the hermetically sealed envelope, whereas the three sets of every third scanning electrodes 112, 115, ...;113,116, .;and 114,117, are respectively connected to the scanning terminals 162, 163, and 164 provided also outside of the envelope.

The common electrode 140 is connected, outside the envelope, to the positive electrode of a DC power supply 143 through a current-limiting resistor 141 and a variable-resistance element 142 provided with a control input terminal 144.

A video signal incoming through a signal input terminal 165 is amplified by an amplifier 145 and the amplified video signal is applied between the backing electrode and ground as a negative polarity voltage.

The video signal is also applied to the control input terminal 144 to control the resistance value of the variable-resistance element 142 in response to the magnitude of the video signal.

Shunt resistors 151' through 157 and so on are respectively connected to the recording stylus electrodes 131 through 137 and so on, andthese shunt resistors are grounded in common. The shunt resistors 151 through 157 and so on are provided to reduce the adverse effects of the stray capacitances that inevitably exist between the recording stylus electrodes and ground.

A start pulse 171 of positive polarity as illustrated is applied to the terminal 161. Likewise, scanning pulses 172, 173, 174, all of positive polarity, are respectively applied to the scanning terminals 162, 163, and 164.

While the structure of the electrostatic device of this invention has been described, its operation will now be described.

lt is assumed that a start pulse 171 is applied at time t, to the scan terminal 161. Then the voltage of the scan terminal 111 with respect to ground is 0, whereas all of the scan electrodes 112, 113, connected to the terminals 162, 163, and 164 are successively maintained at V volts by the scanning pulses 172, 173, and 174.

Accordingly, only the scanning electrode 111 maintains the greatest voltage difference with respect to the common electrode 140 to which a DC voltage of the DC power supply 143 is applied.

If this voltage difference is greater than the discharge triggering voltage, an initial discharge occurs on the scan electrode 111 only and the voltage with respect to the common electrode is maintained at a value equal to the discharge-maintaining voltage, that is, the voltage of the DC power supply 143 minus a voltage drop through the current-limiting resistor 141 and the variable-resistance element 142 caused by a discharge current. As long as the voltage scanning pulses are held as they are, the electric discharge stays where it is at the scanning electrode 111, and in the spaces adjacent the successive scanning electrodes 112, 113, the ions produced'by the discharge at the scanning electrode 111 distribute with gradually decreasing density along the direction of these successive discharge spaces.

It has been known that the discharge triggering voltage of a discharge triggering voltage of a discharge tube decreases with the increase in ion density to approach the discharge maintenance voltage in the presence of the ionized gas molecules in the discharge space prior to the occurrence of an electric discharge.

Accordingly, at time the voltage of the start pulse rises to V volts and the potential difference between the scanning electrode 111 and the common electrode 140 becomes lower than the discharge maintenance voltage at that instant. Thus, the discharge disappears. In this case, the scan electrodes 112, 115, connected to the scan terminal 162 are maintained at volt, or at the ground potential, and the scan electrodes 113, 114, 116, 117, connected to the scan terminals 163 and 164 are all maintained at V volts. Thus, every third scanning electrode 112, 115, connected in common to the scanning terminal 162 can maintain the maximum potential difference with respect to the common electrode 140. Although these scanning electrodes maintain an equal potential difference with respect to the common electrode 140, an electric discharge takes place only on the scanning electrode 112 because the ion density accompanying the discharge is the greatest for the scanning electrode 112 which is located closest to the electrode 111. Consequently, during each repetition period after time t;,, the discharge 4 is sequentially transferred to the scanning electrodes 113, 114, and so on before the resumption of the application of a start pulse 171 on the scanning electrode 111.

Scanning speeds due to the transfer of a discharge are possible up to a maximum of 5 microseconds per hit, which may be converted into a scanning rotation speed of about 26,000 revolutions per minute when the full width of a .llS-B6 format (Japanese lndustrial Standard) is scanned at the line density of 4 lines per millimeter. Therefore, the previous value is considered to be extremely high as compared with the mechanical scanning speeds.

Now, each of voltage pickup electrodes 121 through 127 and so forth disposed respectively adjacent the scanning electrodes produces a voltage at a position in the discharge space where the pickup electrode is located by the ionic conduction that has taken place by the discharge. This voltage s app oximately proportional to the cathode drop voltage in the discharge tube.

The picked up voltages are derived outside the envelope through the recording stylus electrodes 131 through 137 and so forth for the application to the front surface of the electrostatic recording medium 180.

On application of a video signal voltage of negative polarity synchronized with scanning and amplified by an amplifier to the backing electrode which is in contact with the back surface of the recording medium 180, a recording voltage equal to the difference between the pickup electrode voltage and the video signal voltage is applied to that position of the recording medium with which the recording stylus comes into contact, which is associated with the scanning electrode on which the discharge. is taking place. As a consequence, a latent electrostatic image corresponding to the recording voltage is developed. The latent image can be made visible and the recording is accomplished by following the known processes of development and fixation as used for conventional electrostatic recording.

It has been considered that the recording voltages ranging from 500 to 800 volts are necessary in order to obtain recordings of sufficient densities and contrast With the electrostatic. recording device of this invention, the recording voltage becomes less than the above-mentioned voltage (500 to 800 volts) by an amount equal to the pickup electrode voltage and hence, much less than the voltage of a power supply used for the electrostatic printing tube. Specifically, the pickup electrode voltage may be of the order of 200 to 300 volts.

The voltage developed at each recording stylus electrode is simultaneously charged by stray capacitance which inevitably appears between the recording stylus electrode and ground, and the amountof electrical energy stored therein continues discharge with a certain time constraint even after the discharge at one scanning electrode has been shifted tothe next.

When the time constant is greater than the scanning pulse duration, the resolution is deteriorated. Therefore, the shunt resistors 151 through 157 and so forth are interposed to minimize the time constant, thereby reducing the adverse effect of the stray capacitances. An actual method for forming these voltage pickup electrodes is depicted in a perspective view shown in FIG. 2. As illustrated, an array of scanning electrodes 201 and so forth and an array of voltage pickup electrodes 203 and so forth are formed, in one-to-one correspondence, on the same insulating shield 200 in such a manner that one end of each voltage pickup electrode is disposed in the notch 202 cut in one end of the corresponding scanning electrode so as to produce a small clearance therebetween. Such an electrode arrangement has been found simplest and most economical for providing both efficiency of picking up spatial potentials and facilitation of manufacturing through the use of well-known photoetching techniques.

The bombardment of a cathode electrode by positive ions and the subsequent emission of metallic atoms released from the cathode in the surrounding space known as sputtering has been very common with discharge tubes. This phenomenon easily results in the deterioration of the dielectric strength of the surrounding space and the entrapping of gas molecules in the cathode surface, eventually making the device inoperative.

The electrostatic recording device of this invention is no exception to this rule; the scanning electrode, or the cathode, gives rise to sputtering causing degradation in dielectric strength with respect to the voltage pickup electrode and the life span of the device to be shortened.

The method has been used of reducing the sputtering in a discharge tube, such as a display tube, by the addition of a saturated mercury vapor to an inert gas in a hermetically sealed envelope. This method has been found to be effective as applied to the present device.

It has been experimentally determined that sputtering increases as the 3rd power of the discharge current. See, for example, Discharge Tubes by Y. Hatta, published by the Kindai Kagaku sha in 1962, page 82, FIG. 3.25. Therefore, a discharge tube must be operated at as small a discharge current as possible in order to reduce the sputtering.

Our experiments have shown that the discharge current range for a stabilized scanning operation with this electrostatic recording device is ofthe order of from 1 to 5 milliamperes, subject to change by the dimensions of each electrode. Therefore, the ratio of maximum to minimum sputtering amount in this current range (or 1:5) becomes 1:125. Insofar as this problem is concerned, a discharge current of about 5 milliamperes has been found to be appropriate to derive a most practicable voltage.

A facsimile signal has a great deal of redundancy, the proportion of black signals to the entire signals being considerably small. In the absence of the video signal, therefore, there is no need for deriving a voltage from the voltage pickup electrode; the mere scanning operation is all that is needed, whereas the conduction of a discharge current is only needed in the presence of a video signal.

Since video signals used for facsimile, for example, need to be binary signals represented by a logic 1 or 0, the above-mentioned control becomes even easier.

The variable-resistance element 142, which may be a transistor, shown in FIG. 1 serves to variably control the discharge current in response to the video signal. One implementation of the element 142 is schematically illustrated in FIG. 3.

In FIG. 3, reference numerals 140 and 141 denote respectively the common electrode (anode) and the current-limiting resistor as mentioned in connection with FIG. 1. Reference numeral 301 denotes a transistor as the variable resistance element 142 inserted in series with the current-limiting resistor 141 connected in the discharge current path. Reference numeral 303 denotes a shunt resistor connected from the collector to the emitter of transistor 301. Reference numeral 302 denotes a pulse transformer for insulating a video signal source 305 from the DC power supply 143 in the collector circuit of transistor 301 and for applying a video signal to the base electrode of the transistor 301. Reference numeral 304 denotes a damping resistor connected across the secondary of transformer 302, and reference numeral 306 denotes a resistor connected in series to the base of the transistor.

When the output of the video signal power source 305 is a logic 0, the output of the secondary winding of the pulse transformer 302 is equally a logic 0, with the result that the transistor is turned off and its equivalent internal resistance is extremely high.

As a consequence, the discharge current is limited only by the resultant resistance equal to the sum of the resistances of the current-limiting resistor 141 and the shunt resistor 303 connected in series therewith. It will be understood, therefore, that the resistance of both resistors should be set to achieve a minimum current to provide a stabilized discharge scanning operation.

When the video signal voltage becomes a logic 0, the transistor is turned ON and hence, the shunt resistor 303 is short-circuited. Therefore, the discharge current is restricted only by the current-limiting resistor 141. The resistance value of the current-limiting resistor should be set at a value capable of furnishing a maximum current, or a sufficient output voltage, to each recording stylus electrode.

In this way, the discharge current can be controlled in response to the magnitude of the video signal, whereby the greater the proportion of white signals occupying in the entire signals, the longer the device will last.

It has been known that a discharge occurs in a discharge tube at some restricted portion of the cathode electrode surface when the operating current for sustaining a normal glow discharge remains at a small value. By the restricted portion is meant where the electric field intensity is the highest.

In an actual example of an electrode arrangement as shown in FIG. 2, the common electrode 205 faces that portion of the scanning electrode 201, considerably apart from the rectangular notch portion 202 as illustrated. Therefore, an electric discharge will occur between the common electrode and that portion of the scanning electrode located just beneath the common electrode when the discharge current is small.

Such an arrangement contributes greatly to retarding the aging and deterioration in insulation between the scanning and voltage pickup electrodes. In the presence of a video signal, a discharge will take place over the entire scanning electrode surface as a result of an increase in discharge current and hence in discharge area.

Experimental evidence indicates that short-circuiting between the scanning electrode and the corresponding voltage pickup electrode due to sputtering can be effectively prevented by suitably selecting their relative positions.

Referring to FIG. 4, all of the scanning electrodes 411 through 417 and so forth, each provided with a notch cut in one end thereof, the voltage pickup electrodes 421 through 427 having their ends projecting into the respective notches cut in the scanning electrodes, the recording stylus electrodes 431 through 437 respectively connected to the voltage pickup electrodes, the scanning terminals 451 through 454, and the lead wires 442 through 444 to which the three sets of every third scanning electrodes are respectively connected can be formed on an insulating shield 401 such as a ceramic or glass material by utilizing well-known integrated circuit techniques; e.g. evaporation, plating, photoetching, screenprinting, etc.

The scanning electrodes 413, 414, 416, 417, and so forth whichcannot be directly connected to the lead wires 443 and 444 are connected thereto through insulated wires 461, 462, 463, 464, and so forth by using the wire bonding method, for example.

In FIG. 4, the 8th and succeeding scanning electrodes, voltage pickup electrodes, and recording stylus electrodes as well as the fifth and succeeding lead wires have been omitted from the illustration for simplicity.

It has been found desirable for the stabilized scanning of the electric discharges that the scanning electrodes be spaced apart at a regular. interval at least of 0.4 millimeter. The spacing or pitch of the successive recording stylus electrodes should be 0.25 millimeter, for instance, for a density of 4 lines per millimeter, although this value is subject to change according to the required recording resolution. ln other words, the pitch of the recording stylus electrodes has been suitably determined before they are aligned at equal intervals at one edge of the insulating shield.

The end surface of the shield at which the recording stylus electrodes are aligned is inclined at a suitable angle with respect to the bottom surface of the insulating shield. This is to secure optimum contact between the stylus electrodes and the electrostatic recording medium.

On the back surface of theupper shield 402, which is also made of a'ceramic or glass material and provided with an exhaust tube 403, the common electrode 470 is disposed so as to face those portions of the array of scanning electrodes considerably removed from the notchportions, and a terminal 471 is connected to the commonelectrode to provide for the connection of the discharge power supply. The common electrode 470 and terminal 471 are formed by integrated circuit techniques as mentioned previously.

Then the insulating upper and lower shields, separated at a predetermined spacing, are bonded together with a suitable sealing compound such as glass along the peripheral portions 481 and 482 to establish a hermetic seal.

Reference numeral 490 denotes the shunt resistances for reducing the effect of the stray capacitances existing between the plurality of scanning electrodes and ground. These shunt resistances are formed by applying a resistive paint on the recording stylus electrodes and then, annealing the paint, for example.

On the resistive paint layer a conductive paint, for instance, is applied to form the electrode 491 for connection to the terminal 492.

The hermetically sealed structure is mounted on evacuation apparatus and thoroughly evacuated through the exhaust tube 403. Then a small amount of an inert gas such as neon, argon, or xenon, or a mixed gas is admitted to bring up the gas pressure inside to a predetermined value and the exhaust tube is sealed off.

It will be apparent that the embodiment of the electrostatic recording device of this invention as shown and described herein is only exemplary and that various modifications can be made in construction and arrangement within the scope of the invention as defined in the appended claims.

I claim:

1. In an electrostatic recording device for facsimile and the like comprising: an envelope adapted to hermetically contain at least one kind of gas for developing a gas discharge; a first plurality of electrodes arranged to cause gas discharges one after another and thereby to provide a spatial scanning by the discharges; a second plurality of electrodes disposed adjacent respective ones of said scanning electrodes for picking up voltages induced at the conductivestate of said gas discharges; at least one common electrode provided opposite to said first plurality of electrodes, said gas discharges occurring between said common electrode and said first plurality of electrodes; a plurality of stylus electrodes each connected at one of their ends to respective ones of said second plurality of electrodes with the other end thereof arranged in a straight line with the corresponding ends of the remaining stylus electrodes on the outside of said envelope and positioned to come. in contact with one surface of a recording medium; variable resistance means connected to said common electrode for controlling the currents of said discharges in response to the level of avideo signal to be recorded; and means for applying said video signal to the other surface of said recording medium, the improvement wherein said first plurality of electrodes each have a notch formed.

in one'end thereof remote from said common electrode and said second plurality of electrodes are disposed in a one-to-one correspondence in the notches formed in said first plurality of electrodes.

2. An electrostatic recording device as recited in claim 1 further comprising scanning means connected to each of said first plurality of electrodes for sequentially applying a potential difference referenced to said common electrode-to each said first plurality of electrodes to thereby establish a scanning action of an electrical discharge. between said first plurality of electrodes and said common electrode.

3. An electrostatic recording device as recited in claim 2 whereinsaid scanning means includes means for connecting a source of voltage to said common electrode through said variable resistance means and voltage pulsing means connected to each of said first plurality at electrodes for sequentially applying voltage pulses thereto, the resulting potential difference between said common electrode in the presence of a video signal and a pulsed electrode in said first plurality of electrodes being sufficient to maintain a gas discharge therebetween.

4. An electrostatic recording device as recited in claim 3 wherein said voltage pulsing means includes first, second and third terminal means, each of saidtervoltage required for scanning.

UNITED STATES PATENT OFFICE CERTIFICATE CORRECTION PATENT NO. 3 ,870,257

DATED March 11, 1975 INVENTOR(S) I Toshio OHKUBO I It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

IN THE TIT LE:

Delete "RECORDING" and insert RECORDER IN THE SPECIFICATION Column 1, in the title delete "RECORDING" and insert: RECORDER Column 3, line 16 after "assumed" insert first line 43 delete "of a. discharge triggering voltage" Signed and sealed this 0th day of June 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer I and Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,870,257

DATED March 11, 1975 |NVENTOR(S) Toshio OHKUBO It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

IN THE TIT LE:

Delete "RECORDING" and insert RECORDER IN THE SPECIFICATION Column 1, in the title delete "RECORDING" and insert RECORDER Column 3, line 16 after "assumed" insert first line 43 delete "of a discharge triggering voltage" Signed and sealed this 0th day of June 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer I and Trademarks 

1. In an electrostatic recording device for facsimile and the like comprising: an envelope adapted to hermetically contain at least one kind of gas for developing a gas discharge; a first plurality of electrodes arranged to cause gas discharges one after another and thereby to provide a spatial scanning by the discharges; a second plurality of electrodes disposed adjacent respective ones of said scanning electrodes for picking up voltages induced at the conductive state of said gas discharges; at least one common electrode provided opposite to said first plurality of electrodes, said gas discharges occurring between said common electrode and said first plurality of electrodes; a plurality of stylus electrodes each connected at one of their ends to respective ones of said second plurality of electrodes with the other end thereof arranged in a straight line with the corresponding ends of the remaining stylus electrodes on the outside of said envelope and positioned to come in contact with one surface of a recording medium; variable resistance means connected to said common electrode for controlling the currents of said discharges in response to the level of a video signal to be recorded; and means for applying said video signal to the other surface of said recording medium, the improvement wherein said first plurality of electrodes each have a notch formed in one end thereof remote from said common electrode and said second plurality of electrodes are disposed in a one-to-one correspondence in the notches formed in said first plurality of electrodes.
 1. In an electrostatic recording device for facsimile and the like comprising: an envelope adapted to hermetically contain at least one kind of gas for developing a gas discharge; a first plurality of electrodes arranged to cause gas discharges one after another and thereby to provide a spatial scanning by the discharges; a second plurality of electrodes disposed adjacent respective ones of said scanning electrodes for picking up voltages induced at the conductive state of said gas discharges; at least one common electrode provided opposite to said first plurality of electrodes, said gas discharges occurring between said common electrode and said first plurality of electrodes; a plurality of stylus electrodes each connected at one of their ends to respective ones of said second plurality of electrodes with the other end thereof arranged in a straight line with the corresponding ends of the remaining stylus electrodes on the outside of said envelope and positioned to come in contact with one surface of a recording medium; variable resistance means connected to said common electrode for controlling the currents of said discharges in response to the level of a video signal to be recorded; and means for applying said video signal to the other surface of said recording medium, the improvement wherein said first plurality of electrodes each have a notch formed in one end thereof remote from said common electrode and said second plurality of electrodes are disposed in a one-to-one correspondence in the notches formed in said first plurality of electrodes.
 2. An electrostatic recording device as recited in claim 1 further comprising scanning means connected to each of said first plurality of electrodes for sequentially applying a potential difference referenced to said common electrode to each said first plurality of electrodes to thereby establish a scanning action of an electrical discharge between said first plurality of electrodes and said common electrode.
 3. An electrostatic recording device as recited in claim 2 wherein said scanning means includes means for connecting a source of voltage to said common electrode through said variable resistance means and voltage pulsing means connected to each of said first plurality at electrodes for sequentially applying voltage pulses thereto, the resulting potential difference between said common electrode in the presence of a video signal and a pulsed electrode in said first plurality of electrodes being sufficient to maintain a gas discharge therebetween.
 4. An electrostatic recording device as recited in claim 3 wherein said voltage pulsing means includes first, second and third terminal means, each of said terminal means being connected to respective alternate third electrodes of said first plurality of electrodes, and means for aPplying first, second and third voltage pulses in repeating time sequence to said first, second and third terminal means, respectively. 